The invention relates to a circuit arrangement suitable for igniting a lamp and comprising a transformer and means for generating pulsatory voltages across a primary winding of the transformer in order to generate ignition pulses by means of a secondary winding of the transformer.
Such a circuit arrangement is known from the German Patent Application 2011663 laid open to public inspection. The circuit described therein is suitable for connection to an AC voltage source and comprises means by which it can be detected whether a connected lamp has or has not ignited. If it is detected after connection to an AC voltage source that the connected lamp has not ignited, an ignition pulse is generated by the circuit arrangement every half cycle of the AC voltage. This ignition pulse has an amplitude which is a multiple of the AC voltage amplitude. A lamp can be efficiently and reliably ignited by means of the known circuit arrangement.
If the known circuit arrangement is connected to the lamp by means of comparatively short connection cables, the amplitude of the ignition pulse generated by the circuit arrangement is hardly influenced by the capacitance of the connection cables. In practice, however, it is often not possible to choose the connection cables to be short. Under such circumstances, the circuit arrangement and the lamp are interconnected by means of comparatively long connection cables. The comparatively long connection cables represent a considerable capacitance, which adversely affects the amplitude of the ignition pulse.
It is generally valid that the amplitude of the ignition pulse should at least have a minimum value, which depends on the lamp, in order to ignite a lamp. The use of ignition pulses having an amplitude which is considerably greater than the required minimum value, however, is undesirable because this adversely affects the life of the lamp and of the ballast circuit coupled to the lamp. Therefore, it is desirable to choose the amplitude of the ignition pulse within comparatively narrow limits.
Since the amplitude of the ignition pulse is to a high degree dependent on the capacitance presented by the connection cables, it is necessary to dimension the known circuit arrangement in dependence on the length and type of the connection cables which will serve as the connection. This implies that different circuit arrangements must be dimensioned for the ignition of one type of lamp, each circuit arrangement being suitable only for use within a restricted range of connection cable lengths between the circuit arrangement and the lamp. This range depends on the type of connection cable which is used.